Traditional polymers rely on stable covalent bonds; however, biochemical systems depend on dynamic transformations of macromolecular structures to perform living functions. Dynamic covalent polymers based on numerous functional groups such as disulfides, thioesters, lactones, carbonates, and acetals have received increasing interest in the past decade. One dynamic covalent bond that has received only limited attention in the field of polymer chemistry but has been widely used in synthetic organic chemistry is dithioacetal. Although dithioacetals are relatively stable, they can be activated by using acid catalysts. Given their straightforward synthesis, tunability, and dynamics, we investigated dithioacetal as a reversible bond in developing recyclable polymers. We synthesized linear polydithioacetals (PDTAs), which exhibited good mechanical strength. Ring-closing depolymerization of PDTAs in refluxing toluene with zinc(II) triflate catalyst yielded a mixture of cyclic dithioacetals of various ring sizes. Acid catalyzed ring-opening polymerization of these cyclic dithioacetal monomers at room temperature afforded the linear PDTAs. These results demonstrated PDTAs as promising candidates for use as polymers capable of chemical recycling to monomers (CRM). In this presentation, we will highlight the syntheses of the PDTAs, efficiencies of the reversible ring-closing and ring-opening processes monitored by <sup>1</sup>H NMR and GPC, the effects of ring-sizes, and the material properties.

Dithioacetal-based chemically recyclable polymers

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ACS Fall 2022

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